BLOA Review - Neurotransmission, Localization, Neuroplasticity

Neuron

Individual cell of the brain and nervous system; responsible for transmitting information

Nerve

A bundle of neurons

Dendrite

Neuron structure, responsible for receiving neurotransmitter messages from neighboring cells

Axon

Neuron structure, carries action potential away from cell body to terminals, to be passed on to next neurons in line

Action potential

Electrical "message" that travels through a neuron; at axon terminals, stimulates release of neurotransmitters into synapse

Threshold

The level of neurotransmitter stimulation required to trigger a new neural impulse in the next neuron -- an "all or nothing" action; either a new AP is generated, or it isn't

Synapse

Gap between two neurons, across which neurotransmitters travel

Myelin sheath

Neuron structure; fatty covering of axon, causes action potentials to travel faster

Axon terminal

Neuron structure; "end" of a neuron where neurotransmitters are contained and released into synapse

Neurotransmitter

Chemical used by a neuron to transmit an impulse across a synapse to another cell

Inhibitory neurotransmitter

Neurotransmitter that increases likelihood of a new action potential “firing” and traveling through the neuron

Excitatory neurotransmitter (a.k.a. agonist)

Neurotransmitter that stimulates receptor sites, speeding up further neurotransmission

Reuptake

An "unreceived" neurotransmitter's reabsorption by the sending neuron

Serotonin

Neurotransmitter involved in mood regulation, sleep, appetite, and anxiety/depression.

Dopamine

A neurotransmitter associated with movement, attention and learning, and the brain's pleasure and reward system

Acetylcholine (ACh)

Neurostransmitter involved in muscle stimulation, learning, and short-term memory.

Antonova, et al (2011)

Investigated the effect of scopolamine on formation of spatial memories -- experimental condition received a scopolamine injection, control received a placebo -- both placed in fMRI and then participated in "arena game," a VR game where they're in an arena and have to wander around to find a pole -- once found, screen blanks for 30 secs, pats. told to rehearse how they found the pole -- then they play again, using their memory from the first time -- then, 4 weeks later, they returned, were placed in opposite conditions, and repeated the process -- scopolamine injections = reduced hippocampus activity -- conclusion = ACH as a neurotransmitter plays important role in formation of spatial memory, and scopolamine is an important ACH antagonist

Fisher, Aron, & Brown (2005)

Studied the role of dopamine in romantic love -- 10 men, 7 women, all of whom reported being "intensely in love" placed in fMRI scanner, then shown a series of photos of people -- some of neutral acquaintances, some of their loved one -- dopamine-producing brain regions were more active when shown photos of loved one, and dopamine is known to be associated with feelings of pleasure -- concluded that dopamine activity in brain plays a role in romantic love

Localization

Concept that different brain regions are particularly involved in various brain functions

Cerebral cortex

Outer layer of the brain, containing hundreds of billions of neurons; associated with higher-level thinking and personality

Amygdala

Brain region located in the midbrain -- most clearly involved in fear and anger responses

Phelps & Sharot (2007)

Studying if there's physiological evidence for flashbulb memories (FBM's) as separate memory type -- 24 NY'ers placed in fMRI scanner, asked to recall 9/11 experiences, and also other, unrelated events from summer of 2001 -- amygdala activity was higher for those who'd been CLOSER to Trade Center on 9/11, compared to those who'd been a little further north -- concluded that amygdala is involved in the formation of FBM's, helping explain why FBM's include strong emotional content

Hippocampus

Seahorse-shaped brain region located in the temporal lobes (left and right), above the ears -- research has made clear that it is crucial in the transferring of SHORT-term memories into LONG-term storage

Retrograde amnesia

Loss of previously-stored memory, usually from the time period before the events causing the memory loss

Anterograde amnesia

Inability to convert new information from short-term memory into the long-term, stored memory

Procedural memory

Memory of how to perform functions, to do a thing

Episodic memory

Memory of life events

Semantic memory

Memory of facts, concepts, meaning

H.M. case study

Patient who had extensive brain surgery to correct epileptic seizures which left him with severe anterograde amnesia -- hippocampus was removed entirely -- intelligence and memory from before the surgery were normal but it was almost impossible for him to create new, permanent memories -- showed that hippocampus plays key role in converting STM to LTM -- ALSO shows the effectiveness of fMRI scans in confirming suspected brain damage, and how that brain damage is responsible for changes in behavior (e.g., memory loss)

Neuroplasticity

The ability within the brain to constantly change both the structure and function of many cells -- happens in response to experience (learning) and/or trauma (actual brain damage or traumatic events)

Stressor

Acute or chronic environmental stimulus that threatens to disrupt physiological balance; begins a stress response

Dendritic branching

The growth of connections between neurons, in response to environmental stimulation (e.g., learning) that results in faster, more efficient neurotransmission

Draganski, et al (2004)

Studied if brain changes in response to learning -- two groups, jugglers and non-jugglers, neither of whom had any juggling experience -- brain scan taken -- then, juggler condition takes 3 months of juggling lessons, non-juggler condition does not -- second brain scan taken -- then, both groups told not to juggle -- finally, third scan taken -- after second scan, juggler group = more gray matter in brain regions associated with physical coordination -- after third scan, juggler group STILL had more gray matter than non-jugglers -- concluded than learning leads to brain growth, showing neuroplasticity at work

Post-Traumatic Stress Disorder (PTSD)

Disorder triggered by a terrifying event - either experiencing it or witnessing it; connected to raised levels of the hormone cortisol and smaller hippocampus size

Bremner, et al (2003)

Studied link between hippocampal size, prolonged stress exposure, and cortisol levels -- some participants had suffered childhood sexual abuse AND been diagnosed with PTSD, some had been abused WITHOUT diagnosis, and some had not been abused at all -- MRI scans taken of all brains -- then, participants completed a memory test -- both abused groups showed deficits in STM -- hippocampus was SMALLER in abused women's groups -- shows clear correlation between abuse (stress), memory issues, and hippocampal size, showing neuroplasticity at work

Agonist

Chemicals (could be actual neurotransmitters, could be man-made substances) that bind to a synaptic receptor and BOOST an receptor's "receptiveness" = boosts neurotransmitter's effect

Antagonist

Chemicals (typically man-made substances) that bind to a synaptic receptor and BLOCK an receptor's "receptiveness" = weakens neurotransmitter's effect